The present invention relates a hoist for mounting on a support surface such as the ground for lifting a load in a direction generally at right angles to the support surface.
Many different designs of hoist are available for mounting in different locations and including different features for different end uses. The present invention is primarily but not exclusively concerned with safety systems by which an operator can enter through a manhole into a tank or pipe for investigation or service. Current regulations require that the operator be attached to a hoist so that in the event any injury or incapacitation, the operator can be returned to the surface by operation of the hoist.
A number of different designs of hoist of this type have been proposed where a base is located on the ground with legs surrounding the entrance hole and a jib portion extending from the base to an upper end where there is provided a cable guide which allows the cable to extend downwardly between the legs into the entrance so that the cable can pass into the underground area through the hole without dragging on the side of the hole. A manually operable winch is conventionally located on the jib portion so that it can be operated to winch the person back to the surface as required.
It is highly desirable that a device of this type be readily portable and therefore light weight is desirable. Often therefore the device is manufactured from aluminum but this is more difficult to weld. In addition it is desirable to manufacture the product simply from a relatively small number of parts which are easily manufactured and assembled to provide the lightweight construction at low cost.
In view of the foregoing, it is an object of the present invention to provide an improved hoist which can be manufactured simply and inexpensively from simple parts of a limited number thus allowing an economic pricing of the hoist.
According to a first aspect of the invention there is provided a hoist for mounting on a support surface for lifting a load in a direction generally at right angles to the support surface, the hoist comprising:
a base member for mounting on the support surface;
a jib portion;
the jib portion having a bottom coupling at a bottom end for attachment to an attachment portion of the base member such that the jib portion is supported thereby;
and a winch mounting for receiving thereon a winch for paying out and drawing in a cable;
the jib portion having a cable guide member at an upper end over which the cable can pass to be guided from the winch over the cable guide member downwardly from the upper end of the jib portion for attachment to a load to be lifted;
the jib portion being shaped such that the upper end is located upwardly from and forwardly of the bottom coupling such that, with the bottom coupling located by the base member on the support structure behind a load to be lifted, the upper end is located above the load to be lifted;
the jib portion being formed by a tubular body extending substantially from the bottom end to the upper end which is smoothly curved with a constant radius of curvature.
Preferably the tubular body is formed in two pieces where one piece has an end slidable into an end of the other so as to adjust a length of the body, with each piece being curved to the same radius of curvature. One piece, preferably the upper piece is of smaller diameter so as to slide inside the other.
Preferably the tubular body has end portions at the bottom end and the upper end which are straight, that is they have no bend following the same radius as the remained to the body. In an arrangement where the body is made in two pieces, each is bent fully up to the overlapping end so that each follows the same curvature, but each is straight at its opposite end.
Preferably the length of the straight portions is less than 10 inches and more preferably of the order of 5 inches so that the curvature extends along as much as possible of the jib portion but leaves the straight end portions for connection to the elements at the respective end without the necessity for accommodating a curvature at the ends. Thus, the bottom coupling is arranged at the bottom straight portion and the cable guide member is arranged at the upper straight portion.
Preferably the base member includes a vertical post portion onto which the bottom coupling is engaged so that this is preferably straight and vertical to match the bottom of the jib portion.
Preferably the winch mounting is on the jib portion at a position above the bottom coupling and preferably below the overlapping join between the two parts.
Preferably the base member includes two horizontal legs each extending outwardly from the attachment portion and defining therebetween a generally V-shape, each of the legs being formed by a tubular leg body extending substantially from an inner end at the attachment portion to an outer end which is smoothly curved with a constant radius of curvature
Preferably each tubular leg body is formed in two pieces where one piece has an end slidable into an end of the other so as to adjust a length of the body, with each piece being curved to the same radius of curvature.
Preferably each tubular leg body has end portions at the inner end and the outer end which are straight so that the overlapping ends are curved at the common curvature. Thus, the inner end of each leg portion is engaged onto a respective one of two straight stub members of the attachment portion and the straight outer end is engaged onto a ground engaging element for supporting the base member.
The ground engaging element may comprise a pivotal foot simply for resting on the ground or it may comprise a wheel for rolling the structure over the ground to a location of use such as at a manhole.
Preferably the base member is generally Y-shaped in plan so as to define a horizontal rear leg portion extending generally opposite to the legs. The rear leg portion may includes, at an end remote from the jib portion, a ground engaging element for supporting the base member which comprises an adjustable leg for adjusting a height of the rear leg portion relative to a support surface for levelling the base member on the support surface relative to the feet or to the wheels.
Preferably the bottom coupling of the jib portion is separable from the attachment portion of the base member for separating the jib portion from the base member. In this arrangement, the apparatus may include a transportation bracket for carrying the separated jib portion and the separated base member. Such a bracket may include a first support member for receiving the bottom coupling of the jib portion and arranged to support the jib portion in a plane standing generally upwardly from the bracket and the bracket including a second support member for receiving the attachment portion of the base member and arranged to support the base member with the base plane generally parallel to the plane of the jib portion.